1. Technical Field
The present invention relates to a technical field in which semiconductor manufacturing, high functional thin film manufacturing and processing are performed using a plasma process. Particularly, the present invention relates to a processing method of particulate dust in plasma generated in a high vacuum enclosure during the plasma process. Further, the processing method includes deliberate control of the particulate dust in plasma.
2. Prior Art
Conventionally, mainly in a field of semiconductor manufacturing, etching processing of a fine pattern on a surface of a substrate such as a silicon wafer and formation of various kinds of functional thin films such as an oxide thin film and a nitride film by surface reforming, plasma chemical deposition or sputtering have been performed extremely accurately by the use of the plasma process.
However, the particulate dust containing clusters generated in the reactive plasma vapor phase has deposited not only on the substrate surface but also on an inner wall surface of the high vacuum enclosure being a reaction enclosure to contaminate the inside of the high vacuum enclosure. Not only the particulates but also particulates flown into plasma due to peeling of a deposition film deposited in this manner are negatively electrified in plasma, electrically trapped by a plasma boundary region on a substrate front surface to flow onto the substrate surface, and thus deteriorating processing accuracy and film quality, which has been a serious problem.
Accordingly, the following methods are used as conventional ones to prevent the particulate dust from mixing into plasma.    (1) Generation of plasma is executed intermittently by pulse discharge to prevent high dissociation of reactive gas and generation of particulate nucleus, and initial particulates are ejected from the vacuum enclosure during a discharge off time to control generation of the particulates in plasma.    (2) The inside of the vacuum enclosure is opened after usage for a predetermined period and the inner wall is entirely cleaned to remove deposit.    (3) The wall surface of the vacuum enclosure is heated to a high temperature (a few hundred degrees ° C.) to control deposition onto the wall surface within a certain level.    (4) The substrate is arranged to face downward or sideward to prevent the particulates from falling onto the substrate, and the number of mobile portions is made as small as possible to prevent generation of the particulates due to peeling.    (5) A groove is formed beside a substrate holder to confine the particulates and the particulates are ejected along the groove by gas flow.
Sufficient effect could not be obtained by the above methods. For example: in method (1), control needs to be executed where plasma is generated intermittently and a processing time in the plasma process lengthens to reduce productivity; in method (2), processing itself needs to be discontinued periodically, by which not only productivity is reduced but also a large amount of cost is required for the cleaning; in method (3), not only much energy is required to heat the wall surface of the vacuum enclosure to the high temperature (a few hundred ° C.), but also peeling from the wall surface is only reduced and the particulate dust generated in plasma cannot be removed; in method (4), although influence of the particulates generated in plasma can be reduced, the problem of peeling from the inner wall of the vacuum enclosure cannot be solved; and in method (5), although both the particulate dust generated in plasma and deposition of the particulate dust onto the wall surface can be prevented, the particulate dust generated cannot be collected and ejected efficiently due to high vacuum of the inside of the vacuum enclosure.
Therefore, the present invention has been created paying attention to the foregoing problems, and its object is to provide a removing method of the particulate dust in plasma and an apparatus thereof, in which the particulate dust generated in plasma is removed efficiently to solve a problem of deposition onto the inner wall of the vacuum enclosure and a deterioration problem of processing accuracy and film quality associated with flowing of the particulates onto the substrate.